Using quantitative electron microscopy, we propose to study the changes in the structure of the heart associated with diabetes mellitus. Three animal models of the disease will be examined for ultrastructural changes both in myocardial cellular organelles and in the microvascular supply of the heart muscle. Quantitative data on the disease state in a) the genetically diabetic Chinese hamster, (b) the streptozotocin-induced diabetic Syrian hamster and (c) the streptozotocin-induced diabetic macaque monkey will be compared in an effort to delineate any "diabetic cardiomyopathy," and to seek to explain the increased morbidity of the diabetic due to cardiac failure.